Re: patch to allow disable of WAL recycling

From: Jerry Jelinek <jerry(dot)jelinek(at)joyent(dot)com>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: patch to allow disable of WAL recycling
Date: 2018-07-11 12:37:00
Message-ID: CACPQ5FoYw6Tz7dQMjWSKndA9iRnHg38RzWTh8QKJ=DyzmHARww@mail.gmail.com
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Alvaro,

I'll perform several test runs with various combinations and post the
results.

Thanks,
Jerry

On Tue, Jul 10, 2018 at 2:34 PM, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
wrote:

> On 2018-Jul-10, Jerry Jelinek wrote:
>
> > 2) Disabling WAL recycling reduces reliability, even on COW filesystems.
>
> I think the problem here is that WAL recycling in normal filesystems
> helps protect the case where filesystem gets full. If you remove it,
> that protection goes out the window. You can claim that people needs to
> make sure to have available disk space, but this does become a problem
> in practice. I think the thing to do is verify what happens with
> recycling off when the disk gets full; is it possible to recover
> afterwards? Is there any corrupt data? What happens if the disk gets
> full just as the new WAL file is being created -- is there a Postgres
> PANIC or something? As I understand, with recycling on it is easy (?)
> to recover, there is no PANIC crash, and no data corruption results.
>
> --
> Álvaro Herrera https://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>

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